1. Field of the Invention
The present invention relates in general to the formation of an integrated circuit including capacitors. In particular, the present invention relates to a method for forming metal capacitors with a damascene process.
2. Description of the Related Art
Capacitors are integrated in various integrated circuits. For example, capacitors can be used as decoupling capacitors to provide improved voltage regulation and noise immunity for power distribution. Capacitors also have wide applications in analog/logic, analog-to-digital, mixed signal, radio frequency circuits and so on.
A conventional method of manufacturing a semiconductor apparatus including a capacitor 20 that is formed of metal-insulator-metal layers is described with reference to FIGS. 1Axcx9c1D. As shown in FIG. 1A, an aluminum layer is deposited on an insulator 12 which contains interconnections and is formed on a silicon substrate having devices (not shown) thereon and therein. The aluminum layer is then patterned by masking and etching to form wires 14a and 14b. As shown in FIG. 1B, an insulator 16 with a tungsten plug 18 (hereafter xe2x80x9cW-plugxe2x80x9d) used to connect the aluminum wire 14a and the to-be-formed capacitor is formed on the aluminum wires 14a and 14b and the insulator 12. As shown in FIG. 1C, a first conductive plate 21, a dielectric layer 22 and a second conductive plate 23 are sequentially deposited on the insulator 16 and the W-plug 18, and then patterned by masking and etching to obtain a capacitor 20. The first conductive plate 21, the bottom electrode, is connected with the aluminum wire 14a through the W-plug 18. Another insulator 26 is deposited on the insulator 16 and the capacitor 20. The insulators 16 and 26 are patterned and W-plug 28a and W-plug 28b are formed therein. As shown in FIG. 1D, an aluminum layer (not shown) is deposited on the insulator 26 and the W-plugs 28a and 28b. The aluminum layer is then patterned by masking and etching to form wires 34a and 34b. The aluminum wire 34a is connected with the second conductive plate 23 through the W-plug 28a. The aluminum wire 34b is connected with the aluminum wire 14b through the W-plug 28b. 
The above-mentioned method for integrating the capacitor 20 into an integrated circuit requires several masking and etching steps to form the capacitor 20, which may increase overall fabrication costs. Moreover, if a greater capacitance of the plane capacitor 20 is required, a greater area of the plane capacitor 20 is needed. This will sacrifice the spaces between the capacitor 20 and the nearby wires and make scaling down difficult. Furthermore, a drop height exists between the capacitor area and the non-capacitor area, resulting in an uneven topography of the insulator 26.
A method of manufacturing a capacitor while simultaneously forming a dual damascene via is disclosed in U.S. Pat. No. 6,025,226. In the ""226 patent, a conductor which is used to form a bottom electrode is deposited in the openings for the via and capacitor. However, the conductor should be sufficiently thick to fill the via opening and sufficiently thin to not planarize the capacitor opening. It is difficult to form such a conductor.
Besides, the aluminum used to fabricate the traditional interconnections cannot satisfy the trends of enhanced integration and speed of data transmission. Copper (Cu) has high electric conductivity to reduce RC delay and can be substituted for aluminum as conducting wires. The use of copper as the conducting wires requires the use of processes, that is, damascene processes, because copper cannot be patterned by etching processes. This is because the boiling point of copper chloride (CuCl2) produced by copper and the chlorine plasma usually used to etch metal is relatively high, about 1500xc2x0 C. Therefore, Cu processes should be used to fabricate an integrated circuit including a capacitor.
It is an object of the present invention to provide a method for forming metal capacitors with a damascene process.
It is another object of the invention to reduce the number of masking and etching steps in manufacturing an integrated circuit including a capacitor.
Yet another object of the invention is to reduce the cost of manufacturing an integrated circuit including a capacitor.
It is a further object of the invention to reduce the drop height existing between the capacitor area and the noncapacitor area.
Still another object of the invention is to provide easily controllable processes of manufacturing an integrated circuit including a capacitor.
Another object of the invention is to use the Cu processes to fabricate the integrated circuit including capacitors to reduce RC delay.
The present invention provides a method for forming a metal capacitor with a damascene process. Before fabricating the thin-film capacitor, a first Cu wire and a second Cu wire, surrounded with a barrier layer and a first sealing layer, are prepared in a first insulator. A second insulator is formed on the sealing layer. An opening is formed in the second insulator and the sealing layer and the first Cu wire is exposed. A first metal layer, a third insulator and a second metal layer are conformally formed, in turn, in the opening on the second insulator. A chemical mechanical polishing process is executed to remove the first metal layer, the third insulator and the second metal layer until the second insulator is exposed; thereby, a bottom electrode, a capacitor dielectric and an upper electrode are formed in the opening respectively. The bottom electrode is connected to the first Cu wire. A fourth insulator having dual damascene patterns is formed over the capacitor and the second insulator.
These and other objects of the present invention will become readily apparent upon further review of the following specification and drawings.